A wireless, passive dosimeter based on a magnetoelastic sensor is proposed for tracking personal exposure to toxic gaseous chemicals such as mercury vapor. Under the excitation of a magnetic field, the magnetoelastic sensor vibrates, generating a secondary magnetic flux that can be remotely detected with a set of magnetic coils. Detection of a particular chemical is achieved by applying a chemical-sensitive coating that causes a shift in the sensor's resonance behavior (resonant frequency) due to the selective absorption of the chemical. The sensor is incorporated into a badge-like dosimeter worn by the user, and exposure to various chemicals is automatically and remotely monitored through a detection device installed at a doorway. In this project, a gold-coated sensor is used to monitor mercury vapor since mercury reacts to the gold coating to form an amalgam, which changes the mass and elasticity of the coating and triggers a shift in the sensor's resonance behavior. Although mercury vapor is the focus of this project, the ultimate goal of this work is to develop a sensor/dosimeter technology to passively and remotely track the exposure levels of various harmful chemicals. The specific aims of this project include {1} fabrication of the mercury-sensitive coating and sensor array assembly, {2} development of the sensor detection system and algorithms to process sensor response, and {3} demonstration of the efficacy of the dosimeter technology for real-world applications. Upon completion, this project will greatly improve the safety of workers in hazardous environments such as manufacturing plants, research labs, medical facilities, and power plants by monitoring the level of personal exposure to mercury vapor. Mercury vapor monitoring is critical since long-term exposure to this heavy metal has been linked to multiple illnesses including mad hatter syndrome, sensitization dermatitis, birth defects, nervous system damage, etc. Current technologies, although capable of assessing mercury exposure levels, are generally inconvenient to use, have a long turnaround time, or are too expensive to widely apply. Proposed here is a new way of tracking chemical exposure, where the user just needs to wear a badge and his/her chemical exposure levels are automatically determined when he/she passes through a detector. This new technique will reduce human error in safeguarding the worker's health since all measurements will be conducted automatically (no need to send the dosimeter to a lab for analysis). In addition, the proposed technology can be extended for simultaneously monitoring multiple chemicals such as acetaldehyde, arsine, benzaldehyde, formaldehyde, isobutyraldehyde, phosgene and phosphine by developing the appropriate chemical-responsive materials for the sensor.